The present invention relates generally to the field of instrumentation and systems for treatment of the spine, and more particularly to a device for flexibly stabilizing the cervical spine.
As with any bony structure, the spine is subject to various pathologies that compromise its load bearing and support capabilities. Such pathologies of the spine include, for example, degenerative diseases, the effects of tumors and, of course, fractures and dislocations attributable to physical trauma. In the treatment of diseases, malformations or injuries affecting spinal motion segments (which include two adjacent vertebrae and the disc tissue or disc space therebetween), and especially those affecting disc tissue, it has long been known to remove some or all of a degenerated, ruptured or otherwise failing disc. In cases in which intervertebral disc tissue is removed or is otherwise absent from a spinal motion segment, corrective measures are indicated to insure the proper spacing of adjacent vertebrae formerly separated by the removed disc tissue.
Commonly, the adjacent vertebrae are fused together using a graft structure formed of transplanted bone tissue, an artificial fusion element, or other suitable compositions. Elongated rigid plates have been helpful in the stabilization and fixation of the spine when used alone or in conjunction with a grafting procedure, especially in the thoracic and lumbar regions of the spine. These plating systems also have the potential advantage of increasing union rates, decreasing graft collapse, minimizing subsequent kyphotic deformity, and decreasing the need for bulky or rigid postoperative immobilization. Additionally, rigid internal fixation systems may improve the overall quality of life of the patient and may provide the opportunity for earlier rehabilitation.
The plating techniques described above have also found some level of acceptance by surgeons specializing in the treatment of the cervical spine. The cervical spine can be approached either anteriorly or posteriorly, depending upon the spinal disorder or pathology to be treated. Many well-known surgical exposure and fusion techniques of the cervical spine are described in the publication entitled Spinal Instrumentation, edited by Drs. Howard An and Jerome Cotler. The primary focus of cervical plating systems has been to restore stability and increase the stiffness of an unstable spinal motion segment. During the development of cervical plating systems, various needs have been recognized. For example, the system should provide strong mechanical fixation that can control movement of the vertebral segments. The system should also be able to maintain stress levels below the endurance limits of the plate material, while at the same time exceeding the strength of the anatomic structures or vertebrae to which the plating system is engaged. Additionally, the system should preferably be capable of accommodating for the natural movement of the vertebrae relative to one another, including torsional movement during rotation of the spine and translational movement during flexion or extension of the spine.
There is increased concern in the spinal medical community that anterior or posterior plating systems may place excessive loads on the vertebrae or graft structure in response to small degrees of spinal motion. See, e.g., K. T. Foley, D. J. DiAngelo, Y. R. Rampersaud, K. A. Vossel and T. H. Jansen, The In Vitro Effects of Instrumentation on Multi-level Cervical Strut-Graft Mechanics, 26th Proceeding of the Cervical Spine Research Society, 1998. If the plating system is used in conjunction with grafting, these loads may promote pistoning, which can ultimately lead to degradation or failure of the graft construct. Additionally, even small degrees of spinal motion can cause significant forces to be placed on the spinal plate and the bone anchor devices which attach the plate to the vertebrae, whether they be bone screws, hooks, etc. These forces may lead to failure of the plate or loosening of the points of attachment between the bone anchors and the vertebrae, thus resulting in the potential loss of support by the plate.
Thus, there is a general need in the industry to provide a device for flexibly stabilizing the spine, and in particular the cervical region of the spine. The present invention meets this need and provides other benefits and advantages in a novel and unobvious manner.
The present invention relates generally to a system for flexibly stabilizing the spine, and more particularly the cervical region of the spine. While the actual nature of the invention covered herein can only be determined with reference to the claims appended hereto, certain forms of the invention that are characteristic of the preferred embodiments disclosed herein are described briefly as follows.
In one form of the present invention, a device is provided for stabilizing at least a portion of a spinal column, comprising a member engaged between at least two vertebral bodies and being at least partially formed of a material capable of exhibiting superelastic characteristics at about body temperature.
In another form of the present invention, a method is provided for stabilizing at least a portion of the spinal column, comprising providing a member at least partially formed of a material capable of exhibiting superelastic characteristics at about body temperature, and engaging the member to at least two vertebral bodies.
In another form of the present invention, a device is provided for stabilizing at least a portion of a spinal column, comprising a rod member engaged to at least two vertebral bodies and being at least partially formed of a shape-memory material capable of exhibiting superelastic characteristics at about body temperature, with the rod member having a length that varies in response to relative displacement between the at least two vertebral bodies.
In another form of the present invention, a system is provided for stabilizing at least a portion of a spinal column, comprising an implant disposed between two adjacent vertebrae, and a member anchored to the two adjacent vertebrae and being at least partially formed of a material capable of exhibiting superelastic characteristics at about body temperature.
It is one object of the present invention to provide a device and method for stabilizing at least a portion of the spine, and more particularly the cervical region of the spine.
Further objects, features, advantages, benefits, and aspects of the present invention will become apparent from the drawings and description contained herein.